Don't import pwd on windows
Don't import pwd on windows

EdwardJKim/nbgrader,jupyter/nbgrader,jhamrick/nbgrader,jupyter/nbgrader,ellisonbg/nbgrader,jupyter/nbgrader,jhamrick/nbgrader,jhamrick/nbgrader,jupyter/nbgrader,jupyter/nbgrader,EdwardJKim/nbgrader,EdwardJKim/nbgrader,ellisonbg/nbgrader,jhamrick/nbgrader,ellisonbg/nbgrader,EdwardJKim/nbgrader,ellisonbg/nbgrader